This invention relates to magnesium reduced titanium tetrahalide catalyst systems.
It is known to utilize true Grignard reagents of the formula RMgX prepared in the presence of an ether to reduce titanium tetrahalide in the production of catalysts. It is also known to produce what is termed in the art a "solventless" Grignard, which is produced by reacting magnesium metal with an organic halide in the presence of a solvent which is designated as a nonsolvating solvent (i.e., an inert noncomplexing diluent) such as a hydrocarbon as distinguished from an ether. The use of true Grignard reagents, i.e., solutions of organomagnesium halide in ether presents serious difficulties, however, in the production of certain catalysts, particularly in the production of olefin polymerization catalysts, in view of the fact that the large amount of ether is difficult to remove and the remaining complexed ether can reduce the effectiveness of olefin polymerization catalyst systems prepared with the thus-treated Grignard reagent.
Because of greater process economics, it is desirable to carry out olefin polymerization reactions, particularly polymerization reactions involving ethylene and predominantly ethylene copolymers, in an inert diluent at a temperature at which the resulting polymer does not go into solution, with the polymer being recovered without elaborate steps to remove the catalyst. In order for this more economical method of manufacture to be feasible from a practical standpoint, the catalyst must be capable of producing polymer in high productivities in order to maintain the residual catalyst level in the final product at a very low level.
Unfortunately, many catalyst preparation techniques which are capable of producing satisfactory catalysts involve difficult and expensive procedures which cancel out part of the benefits obtained from utilizing these catalysts so far as the economics of the process are concerned.